2gig pc2700 ram
radeon x800pro 256mb
With that rig, I'd have never upgraded to Vista. Proc is slow; mem is large, but slow; graphics are old; and sound is okay. Nothing in that rig is current, so you should have expected problems.
If I were you, I would have spent that money on components, rather than software. If you can, return Vista ASAP. You won't need it for a while.